Kyushu Dental University

Bmi1 is a polycomb protein localized in stem cells and maintains their stemness. This protein is also reported to regulate the expression of various differentiation genes. In this study, to analyze the role of Bmi1 during dentinogenesis, we examined the immunohistochemical localization of Bmi1 during rat tooth development as well as after cavity preparation. Bmi1 localization was hardly detected in the dental mesenchyme at the bud and cap stages. After the bell stage, however, this protein became detectable in preodontoblasts and early odontoblasts just beginning dentin matrix secretion. As dentin formation progressed, Bmi1 immunoreactivity in the odontoblasts decreased in intensity. After cavity preparation, cells lining the dentin and some pulp cells under the cavity were immunopositive for Bmi1 at 4 days. Odontoblast-like cells forming reparative dentin were immunopositive for Bmi1 at 1 week, whereas their immunoreactivity was not detected after 8 weeks. We further analyzed the function of Bmi1 using KN-3 cells, a dental mesenchymal cell line. Overexpression of Bmi1 in KN-3 cells promoted mineralized tissue formation. In contrast, siRNA knockdown of Bmi1 in KN-3 cells reduced alkaline phosphatase activity and the expression of odontoblast differentiation marker genes such as Runx2, osterix, and osteocalcin. Additionally, KN-3 cells transfected with siRNA against Bmi1 showed reduced nuclear transition of β-catenin and expression of phosphorylated-Smad1/5/8. Taken together, these findings suggest that Bmi1 was localized in the odontoblast-lineage cells in their early differentiation stages. Bmi1 might positively regulate their differentiation by accelerating Wnt and BMP signaling pathways.

Food texture is a pivotal factor influencing consumer preference, acceptance, and eating experience. Although human sensory studies have underscored the importance of the sensations of springiness and hardness in mastication and swallowing, the underlying mechanisms remain unknown due to the lack of an animal model. We therefore hypothesized that rats can discriminate textures based on mechanical properties‐springiness and hardness‐independent of taste, odor, and visual cues. To investigate texture perception, we evaluated rats' discrimination of agar gels using a conditioned texture aversion paradigm with a two‐bottle preference test. Agar gels at 1%–3% concentrations were cut into 5 mm cubes or strained through a 100‐mesh sieve to form paste. In the two‐bottle preference test comparing 1% and 3% agar cubes, the conditioned stimulus (CS) applied to the cubes induced selective aversion to the CS cubes, but the CS applied to the paste form eliminated this aversion. Moreover, to exclude taste or odor cues, gelatin cubes with physical properties similar to those of the 3% agar cubes were prepared, and conditioning with these gelatin cubes induced aversion to the 3% agar cubes. To eliminate visual cues, resin cubes resembling agar cubes were prepared; however, conditioning with the resin cubes did not produce aversion to agar cubes. These results indicated that aversion learning to the agar cubes was acquired based on textures rather than taste, odor, or visual properties. The newly developed experimental system offers a valuable framework for exploring mechanisms of food texture perception and guiding the development of texturally optimized food products.

Royal jelly (RJ), secreted by honeybees, contains major fatty acids such as 10-hydroxy-2-decenoic acid (10H2DA) and 10-hydroxydecanoic acid (10HDAA), which are considered to contribute to bone metabolism. However, these fatty acids are rapidly metabolized in the liver following ingestion, resulting in 2-decenoic acid (2DA) and sebacic acid (SA), respectively. Therefore, elucidating the roles of these metabolites in bone metabolism is of considerable importance. In this study, we focused and investigated the effects of 2DA and SA on osteoblast differentiation using osteoblast-lineage cells. SA treatment significantly upregulated the expression of osteoblast marker genes whereas 2DA had no apparent effect. In addition, SA enhanced alkaline phosphatase activity, a typical marker of osteoblast differentiation and mineralization.